Collaborative Research: Groundwater Dynamics of a Barrier Island

沿海地下水是饮用水供应和陆地/海洋界面两侧生态系统功能的重要资源。尽管这一资源具有全球重要性，但对沿海地区地下水动态和生物地球化学循环的控制却知之甚少。多种过程驱动淡水和咸水在海岸线流动和混合；这些过程的相对作用尚不清楚。该项目旨在量化不同天气和潮汐条件下沿海界面的地下水流量和化学交换。我们的主要假设是，短暂的高能风暴事件对可渗透的地下沉积物和沿海海洋之间的化学交换有重大影响。堰洲岛将作为一个现场场地，因为堰洲岛的复杂瞬态流动过程与大陆海岸相同，但规模大大缩小。堰洲岛也是海岸线的重要组成部分，而且日益发达。压电计将安装在佐治亚州的Sapelo岛，以监测地下水水头、温度、盐度、镭同位素示踪剂和相关的生物地球化学。将开发变密度流体流动、热传输和溶质传输的数值模型，以帮助解释热学和地球化学数据，并量化与竞争流动过程相关的流体流动模式和速率。这项工作对发达环境中的污染物迁移、沿海含水层的盐水入侵以及盐沼和沿海渔业等环境中的生态系统功能具有直接意义。沿海地下水动态的知识对于理解海平面上升和与气候变化相关的风暴频率变化的影响也至关重要。这项工作补充了萨佩洛岛LTER正在进行的工作。该项目将培训至少两名研究生和三名本科生进行实地考察和科学研究，该项目将与南卡罗来纳州少数民族参与联盟（SCAMP）和东南海洋科学卓越教育中心（COSEE-SE）等项目协调。

Coastal groundwater is a crucial resource for potable water supply and the functioning of ecosystems on both sides of the land/ocean interface. In spite of the global importance of this resource, controls on groundwater dynamics and biogeochemical cycling in coastal settings are poorly understood. Multiple processes drive fresh and saline groundwater flow and mixing at the coastline; the relative roles of these processes are unclear. This project is designed to quantify groundwater flow and chemical exchange at the coastal interface under varying weather and tide conditions. Our primary hypothesis is that brief, high-energy storm events have a major impact on chemical exchange between permeable subterranean sediments and the coastal ocean. A barrier island will serve as a field site because the same complex, transient flow processes operate in a barrier island as on the mainland coast, but at a greatly reduced scale. Barrier islands also stand alone as important and increasingly developed components of the coastline. Piezometers will be installed on Sapelo Island, Georgia, to monitor groundwater hydraulic head, temperature, salinity, radium isotope tracers, and associated biogeochemistry. Numerical models of variable-density fluid flow, heat transport, and solute transport will be developed to aid interpretation of thermal and geochemical data and to quantify fluid flow patterns and rates associated with competing flow processes. This work has immediate implications for contaminant transport in developed settings, saltwater intrusion into coastal aquifers, and ecosystem functions in settings such as salt marshes and coastal fisheries. Knowledge of coastal groundwater dynamics is also critical for understanding the impact of sea level rise and changes in storm frequency associated with climate change. This work complements ongoing work at the Sapelo Island LTER. The project will train at least two graduate students and three undergraduates in fieldwork and scientific research, and the project will coordinate with such programs as the South Carolina Alliance for Minority Participation (SCAMP) and the Center for Ocean Sciences Education Excellence for the southeast (COSEE-SE).